Flexible buffer material as well as preparation method and application thereof

Abstract

The invention relates to a flexible buffer material as well as a preparation method and application thereof, belongs to the technical field of damping materials, and solves one of the problems of non-uniform pressure transmission, insufficient conduction pressure, loose contact between a pressurizing interface and an interface of a to-be-treated material, easiness in damage to the to-be-treated material, poor wear resistance and poor elasticity and ductility in the prior art. The invention discloses a flexible buffering material. The flexible buffering material is of a three-layer structure formed by sequentially stacking a flexible rubber layer, a fiber-reinforced composite interlayer core body and a wear-resistant rubber layer. Wherein the fiber reinforced composite interlayer core body comprises a multi-gradient density unit. The flexible buffer material has excellent wear resistance and elasticity, realizes high-quality pressurized bonding of easily damaged materials, and plays a certain role in protecting to-be-treated materials on the premise of ensuring uniform pressure transmission, tight interface contact and standard conduction pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of shock absorbing materials, and in particular to a flexible buffer material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the aerospace industry, there is an urgent need for materials that are lightweight, high temperature resistant, and high load-bearing. In order to achieve the maximum weight reduction effect and meet the service environment requirements of high temperature resistant, load-bearing, and heat-resistant integration, external heat protection materials and load-bearing structural materials are generally used to form load-bearing and heat-resistant integrated composite components to protect the internal parts of the aircraft. Due to their different functions, the external heat protection layer and the load-bearing layer have different material characteristics. The external heat protection layer uses lightweight insulation materials with low density, soft and fragile texture, and poor impact and compression resistance. The load-bearing layer uses high temperature resistant resin-based composite materials with high specific strength and stiffness, and is prone to deformation. Therefore, the mode of action and transmission effect of molding pressure during the composite molding process of the two are crucial to the molding quality of the components.

[0003] In the prior art, when the lamination process is used to composite the two, it is easy to cause structural damage and uneven bonding of the materials. Even if the buffer material is used as a protective measure, because the existing buffer material cannot be applied to the special material characteristics of the outer heat protection layer, it will still cause uneven pressure transmission effect, affect the internal molding quality of the component, and even damage the material itself. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a flexible buffer material and a preparation method and application thereof, so as to solve one of the problems of existing buffer materials, namely, insufficient wear resistance, poor elasticity and ductility, poor pressure conduction performance, and easy damage to the material to be processed.

[0005] The present invention discloses a flexible buffer material, characterized in that: the flexible buffer material has a three-layer structure stacked in the order of a flexible rubber layer 1, a fiber-reinforced composite sandwich core, and a wear-resistant rubber layer 5;

[0006] Wherein, the fiber reinforced composite sandwich core comprises multiple gradient density units.

[0007] Specifically, the fiber-reinforced composite sandwich core is made of a fiber preform and resin.

[0008] Specifically, the fiber preform is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber.

[0009] Specifically, the resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, organosilicon-modified phenolic resin, boron phenolic resin, and polyarylacetylene resin.

[0010] Specifically, the density is lowest at the junction of the fiber-reinforced composite sandwich core and the flexible rubber layer 1 , and the density is highest at the junction of the fiber-reinforced composite sandwich core and the wear-resistant rubber layer 5 .

[0011] Specifically, the total thickness of the flexible buffer material is 0.6-1.0 mm, the thickness of the flexible rubber layer 1 and the wear-resistant rubber layer 5 are 0.15-0.25 mm respectively, and the thickness of the fiber-reinforced composite sandwich core is 0.3-0.5 mm.

[0012] The present invention also discloses a method for preparing the flexible cushioning material according to any one of claims 1 to 6, comprising the following steps:

[0013] S1: prepare a flexible rubber sheet;

[0014] S2: preparing fiber preforms of different volume densities, cutting them into suitable sizes and stacking them in order of volume density as gradient reinforcements; diluting the resin with a solvent, injecting it into the gradient reinforcements, and obtaining a fiber-reinforced composite sandwich core after drying;

[0015] S3: prepare wear-resistant rubber sheet;

[0016] S4: placing the cut flexible rubber sheet, the fiber-reinforced composite sandwich core, and the wear-resistant rubber sheet in the vulcanization mold in sequence, and obtaining the flexible cushioning material after vulcanization and demoulding.

[0017] Specifically, the step S2 includes: diluting the resin with a solvent to a mass concentration of 10-50%, controlling the injection pressure to 0.01-0.15 MPa, and injecting the diluted resin into the gradient reinforcement body.

[0018] The present invention also discloses a tooling for integrally forming a composite component, the tooling consisting of an upper mold, a buffer pad, and a bottom mold, wherein the buffer pad is made of the flexible buffer material described in any one of claims 1 to 6 or is made of the flexible buffer material prepared by the preparation method described in any one of claims 7 to 8.

[0019] The present invention also discloses an application of the tooling, by which the tooling is used to realize the integrated molding of the composite component through material surface treatment, adhesive coating, pressurization curing and demoulding steps.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The pressure transmission of the buffer material is uniform and sufficient, and it is not easy to damage the material. The buffer material provided by the present invention adopts a sandwich structure of a flexible rubber layer, a gradient fiber reinforced composite sandwich core and a wear-resistant rubber layer. A better pressure transmission effect is provided by multiple gradient density units. When affected by external pressure changes, the changed pressure can be transmitted to the fiber reinforced composite sandwich core through the flexible rubber layer. The preform sandwich produces a certain degree of deformation and absorbs part of the impact energy, so that the pressure in the system is reasonably dispersed, which plays a role in pressure buffering. If the pressure in the system changes suddenly or pulsates, and suddenly changes to the upper limit of the damage of the outer heat protection layer, since the density gradient fiber reinforced composite sandwich core adopts the same fiber weaving structure as the outer heat protection layer, the low-density unit is preferentially destroyed, which plays a better protective role on the material body. Exemplarily, when the material (fiber and resin type) of the sandwich core is the same as that of the material to be treated, when the density gradient distribution of the sandwich core is 0.4~1.0g / cm 3 , then for density greater than 0.4g / cm 3 The outer heat protection layer material (material to be treated) can play a protective role; if the density of the outer heat protection layer is between 0.4 and 1.0 g / cm 3 It can not only play a protective role but also fully transmit pressure, and the buffering effect is better.

[0022] 2. The buffer material provided by the present invention can be arranged between the equipment and the material to be processed, which fully ensures that the equipment interface is in full contact with the material to be processed. The above-mentioned buffer material can also adjust the thickness of the equipment / tooling cavity to ensure that the bonding surface is in full contact and the force is evenly applied, and solve the problem of insufficient contact of the bonding surface and the existence of bubble gaps leading to poor bonding effect. Exemplarily, when preparing a load-bearing and heat-protective integrated composite component, it can compensate for the surface and thickness tolerances of the outer heat-protective layer and the load-bearing layer itself.

[0023] 3. The buffer material provided by the present invention adopts a sandwich structure of a flexible rubber layer, a gradient fiber reinforced composite sandwich core and a wear-resistant rubber layer, and has high elasticity, large deformation, wear resistance and certain fragility (plays a good protective role on the material body). Therefore, it has high safety, applicability and durability.

[0024] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0026] Figure 1 Schematic diagram of the flexible buffer material structure (3-layer fiber preform);

[0027] Figure 2 It is a schematic diagram of a tooling structure for integrally forming a composite component;

[0028] Figure 3 The present invention is a flow chart of a method for integrally forming a heat-resistant load-bearing composite component.

[0029] Reference numerals:

[0030] 1-flexible rubber layer; 2-first density unit (first layer of fiber preform); 3-second density unit (second layer of fiber preform); 4-third density unit (third layer of fiber preform); 5-wear-resistant rubber layer; 6-bottom mold; 7-edge pressure stop limit block; 8-wedge positioning block; 9-bearing layer; 10-outer heat protection layer; 11-buffer pad; 12-upper mold; 13-positioning screw. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0032] The invention discloses a flexible buffer material having a three-layer structure stacked in the order of a flexible rubber layer, a fiber-reinforced composite sandwich core and a wear-resistant rubber layer; wherein the fiber-reinforced composite sandwich core comprises multi-gradient density units.

[0033] Specifically, the fiber-reinforced composite sandwich core is made of a fiber preform and a resin, and is a precured material with a gradual density gradient made of the fiber preform and the resin.

[0034] When in use, the flexible rubber layer of the flexible buffer material of the present invention contacts the bonding equipment (pressurizing device or tooling, etc.) to transfer the equipment pressure to the fiber-reinforced composite sandwich core with a density gradient and then to the product, thereby playing a preliminary pressure buffering and transmission role.

[0035] The fiber-reinforced composite sandwich core with a density gradient contains multiple gradient density units, thus providing a better pressure transmission effect. When affected by external pressure changes, the composite sandwich deforms to a certain extent and absorbs part of the impact energy, thereby reasonably dispersing the pressure in the system and playing a pressure buffering role.

[0036] In actual use, a cushioning material made of a fiber-reinforced composite sandwich core with the same or similar weaving structure and material (fiber type and resin type) as the material to be treated can be selected. Since the two have similar components and structures, the structural strength and density are positively correlated. When the external pressure exceeds a certain limit, the low-density units of the fiber-reinforced composite sandwich core will be destroyed first, thereby providing better protection for the material body.

[0037] For example, when the structure and material (fiber and resin type) of the fiber-reinforced composite sandwich core are the same or similar to those of the material to be processed, the density gradient distribution of the fiber-reinforced composite sandwich core is 0.4 to 1.0 g / cm 3 (If it is a three-layer density unit structure, the density of the three-layer density unit increases or decreases in sequence, which can be 0.4, 0.7, 1.0g / cm 3 ), then for density greater than 0.4g / cm 3 The outer heat protection layer material (material to be treated) can play a protective role; if the density of the outer heat protection layer is between 0.4 and 1.0 g / cm 3 , while playing a protective role, it can fully transmit pressure and has a better buffering effect. If the pressure in the system changes suddenly or pulsates, and suddenly changes to the upper limit of the damage of the outer heat protection layer, since the fiber-reinforced composite sandwich core with a density gradient adopts the same fiber weaving structure as the outer heat protection layer, it will first destroy the low-density units, which plays a better protective role on the material body, so it has higher safety, applicability and durability.

[0038] The wear-resistant rubber layer has excellent wear resistance and a long service life and can withstand long-term friction without being easily worn.

[0039] Specifically, the fiber preform is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber, and the above fibers are commonly used fibers for special materials in the field of aerospace thermal protection.

[0040] Specifically, the resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, silicone-modified phenolic resin, boron phenolic resin, and polyarylacetylene resin, which are commonly used resins for special materials in the field of aerospace thermal protection.

[0041] The combination of the fiber preform and the resin can cover the composition system of most aerospace special external heat protection materials. The fiber-reinforced composite sandwich core formed by the preform is similar to the structure of most aerospace special external heat protection materials. Therefore, within a similar density range, it has similar force conduction performance and similar structural strength, thereby playing a better stress buffering role between the bonding equipment and the external heat protection layer, avoiding the problem of damage to the external heat protection layer due to excessive local stress, fully playing the role of pressure transmission and product protection, and improving product quality and pass rate.

[0042] Specifically, the density at the interface between the fiber reinforced composite sandwich core and the flexible rubber layer is the lowest, and the density at the interface between the fiber reinforced composite sandwich core and the wear-resistant rubber layer is the highest. The order of the flexible buffer material described below from top to bottom is flexible rubber layer, fiber reinforced composite sandwich core, wear-resistant rubber layer.

[0043] The fiber reinforced composite sandwich core has a decreasing density gradient in the thickness direction (i.e., the junction between the flexible rubber layer and the fiber reinforced composite sandwich core is the lowest density unit), which is achieved by a fiber preform with multiple density units. The fiber preform includes n density units in the thickness direction, where n≥3. The density difference between adjacent density units can be determined according to actual needs, and is preferably uniformly distributed within the selected density range, such as the density difference between adjacent density units △ρ=0.3g / cm 3 Ideally, when n is infinite, the density difference between adjacent density units is infinitely small, and the technical effect is optimal at this time, but this is impossible to achieve in actual implementation. Therefore, the density difference between adjacent density units should be determined comprehensively based on the thickness of the fiber-reinforced composite sandwich core and the thickness of the selected single-layer density unit. Generally speaking, the larger n is, the better the cushioning performance and pressure conduction performance.

[0044] Through this density gradient design, on the one hand, the pressure transmission process will be buffered layer by layer, thereby achieving a better pressure conduction effect. On the other hand, the low-density unit has certain vulnerable protection characteristics. If the pressure in the system changes suddenly or pulsates, and suddenly changes to the upper limit of the damage of the outer heat protection layer, since the density gradient fiber reinforced composite sandwich core adopts the same fiber weaving structure as the outer heat protection layer, the low-density unit will be destroyed first, thereby playing a protective role.

[0045] In fact, the fiber reinforced composite sandwich core with a density increasing gradient in the thickness direction (i.e., the junction between the flexible rubber layer and the fiber reinforced composite sandwich core is the unit with the highest density) can also play a certain buffering function, but the buffering effect will be slightly worse.

[0046] Specifically, the total thickness of the flexible buffer material is 0.6-1.0 mm, wherein the thickness of the flexible rubber layer and the wear-resistant rubber layer are 0.15-0.25 mm respectively, and the thickness of the fiber-reinforced composite sandwich core is 0.3-0.5 mm.

[0047] An important application scenario of the flexible buffer material disclosed in the present invention is the preparation of special composite components for aerospace. By pressurizing and bonding the outer heat protection layer and the load-bearing layer, a heat-resistant and load-bearing integrated composite component is obtained. The total thickness tolerance of such components generally does not exceed 0.6mm. In order to ensure the uniformity of pressure transmission and the full fit between the equipment interface and the material interface, the thickness of the buffer material should not be less than the total tolerance size of the material to be processed, that is, 0.6mm. In addition, the thickness of the buffer material should not be too thick. According to practical experience, it is appropriate to not exceed 1mm.

[0048] Preferably, in order to fully ensure the adequacy of pressure transmission and take into account the protection of the material to be treated, the thickness of the fiber reinforced composite sandwich core should not be less than twice the thickness of the flexible rubber layer or the wear-resistant rubber layer. Since the fiber reinforced composite sandwich core can be destroyed in advance when the pressure approaches or exceeds the tolerance limit of the material to be treated, a thicker fiber reinforced composite sandwich core is conducive to leaving more safety protection margin. According to practical experience, considering factors such as pressure transmission and cost, the thickness of the fiber reinforced composite sandwich core should not be unlimitedly thickened, that is, 0.3 to 0.5 mm is appropriate.

[0049] Specifically, the flexible rubber layer is one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, and EPDM rubber. The flexible rubber layer composed of the above materials can meet the requirements of strength ≥ 2.0MPa, elongation ≥ 300%, and elasticity ≥ 60%, has good deformation performance and coating effect, and is conducive to full contact and pressure conduction between interfaces.

[0050] Specifically, the wear-resistant rubber layer is made of one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, EPDM rubber, and added with wear-resistant fillers; the wear-resistant fillers are one or more of carbon fiber, graphite, polytetrafluoroethylene particles, and molybdenum disulfide.

[0051] Preferably, the amount of wear-resistant filler added is 3% to 10% by mass based on the total mass of the wear-resistant rubber layer. If the amount added is too small, it cannot achieve a good wear-resistant effect, and if the amount added is too high, it affects the viscosity and uniformity of the rubber body and affects the vulcanization molding of the rubber layer.

[0052] The present invention also discloses a method for preparing the flexible buffer material, comprising the following steps:

[0053] S1: prepare a flexible rubber sheet;

[0054] S2: preparing fiber preforms of different volume densities, cutting them into suitable sizes and stacking them in order of volume density as gradient reinforcements; diluting the resin with a solvent, injecting it into the gradient reinforcements, and obtaining a fiber-reinforced composite sandwich core after drying;

[0055] S3: prepare wear-resistant rubber sheet;

[0056] S4: placing the cut flexible rubber sheet, the fiber-reinforced composite sandwich core, and the wear-resistant rubber sheet in the vulcanization mold in sequence, and obtaining the flexible cushioning material after vulcanization and demoulding.

[0057] Specifically, the flexible rubber sheet can be purchased or prepared by oneself.

[0058] The present invention provides a method for preparing a rubber sheet, wherein the raw materials for the preparation include a rubber base material, a softener, an anti-aging agent, a toughening agent, and a processing aid, and the method comprises the following steps:

[0059] The prepared raw materials are fully mixed according to the proportion and put into a mixer for mixing, and the rubber rubber mass is obtained after uniform mixing;

[0060] The rubber mass obtained by kneading is calendered to obtain a flexible rubber sheet with a specific thickness and width.

[0061] Exemplarily, the above-mentioned raw materials include, by mass fraction, 70-80% rubber base material, 5-10% softener, 0.5-2% anti-aging agent, 10-20% toughening agent, 1-3% processing aid, and the calendering molding temperature is 60-95°C.

[0062] Preferably, the rubber substrate of the flexible rubber sheet is one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, butadiene rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, and EPDM rubber.

[0063] The flexible rubber layer prepared from the above materials can meet the requirements of strength ≥2.0MPa, elongation ≥300%, and elasticity ≥60%, has good deformation performance and coating effect, and is conducive to full contact and pressure conduction between interfaces.

[0064] Specifically, in step S2, the number of stacked layers of the fiber preform is not less than 3. Using more stacked layers can obtain a smoother density gradient, which is beneficial to the conduction of pressure and the stability of the internal structure of the fiber reinforced composite sandwich core. However, considering that the total thickness of the fiber reinforced composite sandwich core should not exceed 0.5 mm, the number of stacked layers of the fiber preform should not be increased indefinitely.

[0065] For example, along the direction from the wear-resistant rubber layer to the flexible rubber layer, the volume density difference between adjacent fiber preforms (for example, a total of 3 layers) is 0.1-0.2 g / cm3 Controlling the volume density difference between adjacent fiber preforms to be uniformly distributed within the upper and lower density limits is beneficial to improving the structural stability of the flexible buffer material and also helps to obtain a better pressure conduction effect.

[0066] Specifically, the fiber preform is made by fiber mesh, needle punching, composite needle punching or stitching, etc., and has a three-dimensional multi-layer grid structure with a volume density of 0.12-0.4 g / cm 3 The core density of the fiber-reinforced composite sandwich core prepared within this volume density range covers the density range of common thermal protection layer materials, thereby achieving a more adequate pressure transmission effect and protective effect.

[0067] The fiber preform has a porosity greater than 65%. The higher porosity meets the density requirement and facilitates resin impregnation during subsequent precuring. On the other hand, when subjected to external pressure shock in actual applications, the porous mesh structure can effectively absorb external energy, thereby providing a higher stress absorption and buffering effect.

[0068] Specifically, the specific operation of step S2 is to dilute the resin to a mass concentration of 10-50% by solvent, control the injection pressure to 0.01-0.15Mpa and inject it into the gradient reinforcement body. The solvent is one or a mixture of ethanol, isopropanol, water, ethylene glycol or glycerol. The mass concentration is 10-50%. When the mass concentration is too high, the resin cannot be evenly dispersed, affecting the molding effect. When the concentration is too low, the sandwich core of a specific density cannot be prepared, affecting the final material buffering effect.

[0069] The present invention also discloses a tooling for integrally forming a composite component, wherein the composite component is an integrated heat-proof and load-bearing composite component, which is formed by bonding an outer heat-proof layer and a load-bearing layer together; the tooling consists of an upper mold, a buffer pad, and a bottom mold, wherein the buffer pad is made of the above-mentioned flexible buffer material.

[0070] Specifically, the bottom mold is provided with a positioning device, which is composed of an edge pressure stop limit block and a middle wedge-shaped positioning block. The lower surface of the edge pressure stop limit block is provided with a screw structure, which cooperates with the screw hole at the corresponding position of the bottom mold to achieve the connection and fixation of the edge pressure stop limit block and the bottom mold.

[0071] This tooling realizes precise positioning and assembly of the outer heat protection layer and the bearing layer through the cooperation of the edge pressure stop block and the middle wedge-shaped positioning block, and realizes overall high-precision and high-quality bonding molding. What is particularly important is that based on the dual-function design of cavity thickness control and stress buffering, a flexible buffer layer (i.e., buffer pad) is introduced between the composite component and the tooling. On the one hand, it compensates for the surface and thickness tolerances of the outer heat protection layer and the bearing layer itself, controls the cavity thickness, and ensures that the bonding surface is in close contact and the force is uniform; on the other hand, it provides a better stress buffering effect between the upper mold of the tooling and the outer heat protection layer, and has good wear resistance, avoiding the problem of damage to the outer heat protection layer due to excessive local stress, effectively protecting the product, and improving product quality and pass rate.

[0072] Specifically, the buffer pad is fixed to the lower surface of the upper mold by bonding.

[0073] Specifically, the thickness of the above-mentioned buffer pad is 0.6-1.0mm. Generally, the total thickness tolerance of the bearing layer and the outer heat protection layer (material to be treated) is generally not more than 0.6mm. In order to ensure the uniformity of pressure transmission and the full fit between the equipment interface and the material interface, the thickness of the buffer material should not be less than the total tolerance of the material to be treated, that is, 0.6mm. In addition, the thickness of the buffer material should not be too thick. According to actual experience, it is appropriate not to exceed 1mm.

[0074] Specifically, the shapes of the upper mold and the bottom mold match each other, and are plane, specific arc or variable curvature shapes, and the bottom mold is provided with a cavity. The cavity profile matches the bearing layer, and the inner side wall of the cavity fits the side edge of the bearing layer to fix the bearing layer. In other words, the setting of the cavity is closely related to the size and thickness of the material to be processed. Once the size of the cavity is determined, the size and thickness of the material that can be processed by the tooling are also fixed accordingly.

[0075] Specifically, the positioning device is composed of an edge pressure stop limit block and a middle wedge-shaped positioning block. On the one hand, the edge pressure stop limit block is used to fix the material to be processed, effectively preventing the material from being inaccurately positioned due to warping and deformation. At the same time, the limit block is used to determine the edge position of the material around the material, and the position of the material to be processed is roughly adjusted as a pre-positioning reference; and the middle wedge-shaped positioning block is used as a second positioning reference, which can make a more accurate adjustment to the relative position of multiple layers (two layers or more) of the material to be processed, ensuring that the multiple layers of the material to be processed are fixed at the theoretical bonding position.

[0076] Specifically, the bottom surface contour of the edge pressure stop limit block matches the bottom mold and is designed to be a plane, a specific arc or a variable curvature shape. A threaded hole is provided at the corresponding position of the bottom mold, and the limit block is connected to the bottom mold by a fastening screw. Optionally, the number of limit blocks can be 2 or more according to the specific size and shape of the material to be processed.

[0077] Specifically, the middle wedge-shaped positioning block is provided with a threaded hole connected to the bottom mold, and the threaded hole is used to fix the wedge-shaped positioning block to the positioning groove of the bottom mold. When the position of the wedge block is fully matched with the product, the positioning block is aligned with the threaded hole of the bottom mold.

[0078] Preferably, the thickness / height of the edge pressure stop block and the middle wedge-shaped positioning block should not be too large, and the specific size is adjusted as appropriate according to the thickness of the material to be processed to avoid the top of the positioning device being too high, thereby interfering with the bottom surface of the upper mold and causing uneven pressure.

[0079] The present invention also discloses an application of the above-mentioned tooling, namely, an integrated molding method of a heat-resistant and load-bearing integrated composite material component. The above-mentioned tooling is used to achieve the integrated molding of the composite component through the steps of material surface treatment, adhesive coating, pressurized curing, demolding, etc.

[0080] The specific steps include:

[0081] S21: Prepare the load-bearing layer and the outer heat protection layer;

[0082] S22: roughening the bonding surface of the bearing layer and the outer heat protection layer;

[0083] S23: placing the bearing layer on the tooling bottom mold, and pre-positioning and fixing it;

[0084] S24: applying adhesive to the bonding surface of the bearing layer and the outer heat protection layer, placing the outer heat protection layer on the bearing layer, positioning and fixing it, and closing the upper mold with the buffer pad bonded to the lower surface;

[0085] S25: placing the tooling on the press, setting press parameters, and pressurizing and curing;

[0086] S26: Take out the tooling, demould, and obtain the composite material component.

[0087] Specifically, the bearing layer in step S21 is a high temperature resistant resin such as bismaleimide, polyimide, etc., and the corresponding prepreg is prepared by a hot melt method or a wet method, and the composite material bearing layer is prepared by a molding process or an autoclave molding process.

[0088] Specifically, the outer heat protection layer is a composite material made of fiber preforms impregnated with resin glue, and the fiber preforms are molded in a molding mold, and the resin precursor glue is injected under pressure. After the composite is fully impregnated, it is cured and dried to obtain the outer ablation layer. The above materials are all materials disclosed by existing technologies and can be purchased or prepared according to actual needs.

[0089] Specifically, the fiber preform of the outer heat protection layer is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber, and the above fibers are commonly used fibers for special materials in the field of aerospace thermal protection.

[0090] Specifically, the resin used in the outer heat protection layer is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, silicone-modified phenolic resin, boron phenolic resin, and polyarylacetylene resin. The above resins are commonly used resins for special materials in the field of aerospace thermal protection.

[0091] Specifically, step S22 may roughen the bonding surface by surface grinding, sandblasting or other processes, thereby increasing the roughness of the bonding surface, making it more fully in contact with the adhesive and having a larger contact area, which is conducive to obtaining a better bonding effect.

[0092] Preferably, the bonding surface of the bearing layer is sandblasted with diamond sand of less than 50 mesh; the bonding surface of the outer heat protection layer is polished with sandpaper of less than 50 mesh. When the sandblasting and polishing mesh is too high, the surface roughness is lower and the surface roughening effect cannot be achieved. When the mesh is too low, the surface quality will be more rough and uneven, which will damage the performance of the material itself.

[0093] Specifically, the specific operation of step S23 is to place the bearing layer on the tooling bottom mold, make the inner surface fit with the bottom mold surface, fix it with the edge pressure stop limit block, and then test-assemble the outer heat protection layer, use the edge pressure stop limit block as a pre-positioning reference to determine the circumferential edge position, and align, position, and adjust it. This step only pre-positions and fixes the bearing layer, and the test assembly of the outer heat protection layer is only to assist in verifying whether the pre-positioning effect of the bearing layer is ideal.

[0094] Specifically, the specific operation of step S24 is to place the outer heat protection layer on the bearing layer, use the wedge-shaped positioning block to position it, so that the positions of the bearing layer and the outer heat protection layer match, and fix the position of the outer heat protection layer after assembling it in place. In fact, the wedge-shaped positioning block will perforate the center of the bearing layer and the outer heat protection layer, and the final molded product generally needs to be cut and used, and the perforated area is discarded.

[0095] Specifically, the adhesive in step S24 is silicone rubber, silicon oxide nitrogen glue or other adhesives with good heat resistance and bonding properties. The temperature resistance level of this type of adhesive is above 300°C, which meets the use temperature requirements. The coating thickness is 0.5 to 1mm. If the adhesive layer is too thin, it cannot penetrate both sides of the bonded object or even only has glue on one side, which has a negative impact on the internal bonding quality. If the adhesive layer is too thick, the probability of defects inside the adhesive layer increases, and when subjected to external force, it is easy to cause stress concentration around these defects, resulting in subsequent product damage to the adhesive layer in a high heat flow service environment.

[0096] Specifically, the press parameters are pressurized at 1.5MPa to 3MPa. When the bonding pressure is too high, it is easy to damage the external heat-resistant material, causing irreversible structural damage such as delamination and fracture. When the bonding pressure is too low, the adhesive cannot flow effectively inside the material, affecting the wetting effect on the bonding surface and having an adverse effect on the bonding effect.

[0097] Specifically, the curing temperature is room temperature to 60°C. When the temperature is too high, the outer heat protection layer is easily affected by the temperature and chemical reactions occur, which will destroy the main body structure and affect the subsequent service performance.

[0098] Specifically, the specific operation of step S25 is to open the upper mold after curing at room temperature for 72 hours, loosen the fastening screws of the edge pressure limit block and the middle wedge-shaped positioning block respectively, remove the positioning block, clean the residual adhesive and perform local trimming to obtain the product after bonding.

[0099] Embodiment and comparative example:

[0100] Example 1

[0101] Step 1: Preparation of flexible rubber layer

[0102] 78% nitrile rubber, 8% softener, 1% anti-aging agent, 10% toughening agent, and 3% processing aid are fully mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber mass is obtained. The rubber mass obtained by mixing is calendered at a calendering temperature of 70°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0103] Step 2: Preparation of fiber reinforced composite sandwich core

[0104] The low-density fiber preform adopts the phenolic fiber mesh composite needle punching process, and the first density unit volume density is 0.14g / cm 3 The volume density of the second density unit is 0.25g / cm 3 The volume density of the third density unit is 0.30g / cm 3 The gradient fiber preform was used as the reinforcement, the resin was diluted with ethanol solvent, the mass concentration was controlled to be 25%, and it was injected into the reinforcement for sol-gel reaction. The injection pressure was controlled to be 0.10MPa. After drying at normal pressure, the fiber-reinforced composite sandwich core was obtained. The density of the fiber-reinforced composite sandwich core ranged from 0.50 to 0.80g / cm 3 .

[0105] Step 3: Preparation of wear-resistant rubber layer

[0106] 75% nitrile rubber, 8% softener, 1% anti-aging agent, 10% toughening agent, 2% processing aid, and 4% polytetrafluoroethylene particle wear-resistant filler are fully mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber rubber mass is obtained. The rubber rubber mass obtained by mixing is calendered at a calendering temperature of 70°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0107] Step 4: Preparation of flexible buffer layer

[0108] First, preheat the vulcanization mold to 150-180°C, lay a layer of flexible rubber sheet on the mold, and then lay the fiber-reinforced composite sandwich core. The volume density of the fiber-reinforced composite sandwich core is 0.14g / cm 3 The third density unit is connected to the flexible rubber sheet, and finally the surface wear-resistant rubber sheet is laid, the mold is covered, and the vulcanization stage is entered. The vulcanization temperature is 180℃ and maintained for 4 hours. After demolding, a 1mm thick flexible buffer layer is obtained.

[0109] The above-mentioned flexible buffer material is used to bond the outer heat protection layer to the bearing layer.

[0110] Prepare tooling, including upper mold, cushion and bottom mold;

[0111] The above-mentioned tooling is used to bond the outer heat protection layer to the bearing layer to prepare a composite component, and the steps are as follows:

[0112] Step 1: Prepare the bearing layer and outer heat protection layer:

[0113] The bearing layer is made of carbon fiber reinforced polyimide resin and is prepared by a molding process;

[0114] The outer heat protection layer is a composite material made of uniform phenolic fiber preform impregnated with phenolic resin glue, with a density of 0.60g / cm 3 .

[0115] Step 2: Roughening:

[0116] The outer surface of the bearing layer is sandblasted with 50-mesh corundum sand, and the inner surface of the outer heat-proof layer is polished with 50-mesh sandpaper. After cleaning, it is set aside.

[0117] Step 3: Place the bearing layer on the tooling bottom mold and pre-position and fix it:

[0118] Place the bearing layer in the cavity of the tooling bottom mold so that the inner surface fits with the bottom model surface and fix it with the edge pressure stop block. Then try to assemble the outer heat protection layer and use the edge pressure stop block as a pre-positioning reference to determine the circumferential edge position for alignment, positioning and adjustment.

[0119] Step 4: Bonding and molding:

[0120] Evenly apply KH-RTV-400 silicone rubber adhesive with a total thickness of 0.5 mm on the bonding surface of the bearing layer and the outer heat protection layer, place the outer heat protection layer on top of the bearing layer, use the second positioning reference to position it, fix the position of the outer heat protection layer after assembling it into place, close the upper mold of the tooling and install it on the press.

[0121] Step 5: Pressurized curing with a bonding pressure of 2 MPa to complete the bonding and forming of the heat-resistant and load-bearing integrated composite component.

[0122] Step 6: Demolding:

[0123] After curing at room temperature for 72 hours, open the upper mold, loosen the fastening screws of the edge pressure limit block and the middle wedge-shaped positioning block respectively, take out the positioning block, clean the residual adhesive and perform local trimming to obtain the bonded product.

[0124] Implementation Effect

[0125] The prepared flexible buffer material has a strength of 3.0 MPa, an elongation of 350%, and an elasticity of 75%.

[0126] The product was tested using CT and the bonding quality of the bearing layer and the outer heat protection layer was good, with no debonding areas, the effective bonding area ratio was 100%, and the structures of the outer heat protection layer and the bearing layer were intact without any internal damage.

[0127] Example 2

[0128] Step 1: Preparation of flexible rubber layer

[0129] 80% butadiene rubber, 6% softener, 2% anti-aging agent, 10% toughening agent, and 2% processing aid are mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber mass is obtained. The rubber mass obtained by mixing is calendered at a calendering temperature of 65°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0130] Step 2: Preparation of fiber reinforced composite sandwich core

[0131] The low-density fiber preform adopts a glass fiber mesh composite needle punching process, and the first density unit volume density is 0.10g / cm 3 The volume density of the second density unit is 0.22g / cm 3 The volume density of the third density unit is 0.30g / cm 3The gradient fiber preform was used as the reinforcement, the resin was diluted with ethanol solvent, the mass concentration was controlled to be 25%, and it was injected into the reinforcement for sol-gel reaction. The injection pressure was controlled to be 0.10MPa. After drying at normal pressure, the fiber-reinforced composite sandwich core was obtained. The density of the fiber-reinforced composite sandwich core ranged from 0.40 to 0.80g / cm 3 .

[0132] Step 3: Preparation of wear-resistant rubber layer

[0133] 78% butadiene rubber, 6% softener, 2% anti-aging agent, 8% toughening agent, 2% processing aid, and 4% polytetrafluoroethylene particle wear-resistant filler are fully mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber agglomerate is obtained. The rubber agglomerate obtained by mixing is calendered at a calendering temperature of 65°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0134] Step 4: Preparation of flexible buffer layer

[0135] First, preheat the vulcanization mold to 150-160°C, lay a layer of flexible rubber sheet on the mold, and then lay the fiber-reinforced composite sandwich core. The volume density of the fiber-reinforced composite sandwich core is 0.10g / cm 3 The third density unit is connected to the flexible rubber sheet, and finally the surface wear-resistant rubber sheet is laid, the mold is covered, and the vulcanization stage is entered. The vulcanization temperature is 160℃ and maintained for 4 hours. After demolding, a 1mm thick flexible buffer layer is obtained.

[0136] The above-mentioned flexible buffer material is used to bond the outer heat protection layer to the bearing layer.

[0137] Prepare tooling, including upper mold, cushion and bottom mold;

[0138] The above-mentioned tooling is used to bond the outer heat protection layer to the bearing layer to prepare a composite component, and the steps are as follows:

[0139] Step 1: Prepare the bearing layer and outer heat protection layer:

[0140] The bearing layer is made of carbon fiber reinforced bismaleimide resin and is prepared by a molding process;

[0141] The outer heat protection layer is a composite material made of glass fiber preform impregnated with phenolic resin glue, with a density of 0.70g / cm 3 .

[0142] Step 2: Roughening:

[0143] The outer surface of the bearing layer is sandblasted with 50-mesh corundum sand, and the inner surface of the outer heat-proof layer is polished with 50-mesh sandpaper. After cleaning, it is set aside.

[0144] Step 3: Place the bearing layer on the tooling bottom mold and pre-position and fix it:

[0145] Place the bearing layer in the cavity of the tooling bottom mold so that the inner surface fits with the bottom model surface and fix it with the edge pressure stop block. Then try to assemble the outer heat protection layer and use the edge pressure stop block as a pre-positioning reference to determine the circumferential edge position for alignment, positioning and adjustment.

[0146] Step 4: Bonding and molding:

[0147] Evenly apply KH-RTV-400 silicone rubber adhesive with a total thickness of 0.5 mm on the bonding surface of the bearing layer and the outer heat protection layer, place the outer heat protection layer on top of the bearing layer, use the second positioning reference to position it, fix the position of the outer heat protection layer after assembling it into place, close the upper mold of the tooling and install it on the press.

[0148] Step 5: Pressurized curing with a bonding pressure of 2 MPa to complete the bonding and forming of the heat-resistant and load-bearing integrated composite component.

[0149] Step 6: Demolding:

[0150] After curing at room temperature for 72 hours, open the upper mold, loosen the fastening screws of the edge pressure limit block and the middle wedge-shaped positioning block respectively, take out the positioning block, clean the residual adhesive and perform local trimming to obtain the bonded product.

[0151] Implementation Effect

[0152] The prepared flexible buffer material has a strength of 3.5 MPa, an elongation of 340%, and an elasticity of 82%.

[0153] The product was tested using CT and the bonding quality of the bearing layer and the outer heat protection layer was good, with no debonding areas, the effective bonding area ratio was 100%, and the structures of the outer heat protection layer and the bearing layer were intact without any internal damage.

[0154] Example 3

[0155] Step 1: Preparation of flexible rubber layer

[0156] 78% silicone rubber, 8% softener, 1% anti-aging agent, 10% toughening agent, and 3% processing aid are fully mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber mass is obtained. The rubber mass obtained by mixing is calendered at a calendering temperature of 85°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0157] Step 2: Preparation of fiber reinforced composite sandwich core

[0158] The low-density fiber preform adopts the phenolic fiber mesh composite needle punching process, and the first density unit volume density is 0.12g / cm 3 The volume density of the second density unit is 0.26g / cm 3 The volume density of the third density unit is 0.36g / cm 3 The gradient fiber preform was used as the reinforcement, the resin was diluted with ethanol solvent, the mass concentration was controlled to be 25%, and it was injected into the reinforcement for sol-gel reaction. The injection pressure was controlled to be 0.10MPa, and the fiber-reinforced composite sandwich core was obtained after drying at normal pressure. The density of the fiber-reinforced composite sandwich core ranged from 0.44 to 0.85g / cm 3 .

[0159] Step 3: Preparation of wear-resistant rubber layer

[0160] 75% silicone rubber, 8% softener, 1% anti-aging agent, 10% toughening agent, 2% processing aid, and 4% molybdenum disulfide wear-resistant filler are fully mixed in proportion and put into a mixer for mixing. After uniform mixing, a rubber rubber mass is obtained. The rubber rubber mass obtained by mixing is calendered at a calendering temperature of 85°C to obtain a flexible rubber sheet with a fixed thickness and width.

[0161] Step 4: Preparation of flexible buffer layer

[0162] First, preheat the vulcanization mold to 150-180°C, lay a layer of flexible rubber sheet on the mold, and then lay the fiber-reinforced composite sandwich core. The volume density of the fiber-reinforced composite sandwich core is 0.12g / cm 3 The third density unit is connected to the flexible rubber sheet, and finally the surface wear-resistant rubber sheet is laid, the mold is covered, and the vulcanization stage is entered. The vulcanization temperature is 180℃ and maintained for 4 hours. After demolding, a 1mm thick flexible buffer layer is obtained.

[0163] The above-mentioned flexible buffer material is used to bond the outer heat protection layer to the bearing layer.

[0164] Prepare tooling, including upper mold, cushion and bottom mold;

[0165] The above-mentioned tooling is used to bond the outer heat protection layer to the bearing layer to prepare a composite component, and the steps are as follows:

[0166] Step 1: Prepare the bearing layer and outer heat protection layer:

[0167] The bearing layer is made of carbon fiber reinforced polyimide resin and is prepared by a molding process;

[0168] The outer heat protection layer is a composite material made of uniform phenolic fiber preforms impregnated with phenolic resin glue, with a density of 0.68g / cm 3 .

[0169] Step 2: Roughening:

[0170] The outer surface of the bearing layer is sandblasted with 50-mesh corundum sand, and the inner surface of the outer heat-proof layer is polished with 50-mesh sandpaper. After cleaning, it is set aside.

[0171] Step 3: Place the bearing layer on the tooling bottom mold and pre-position and fix it:

[0172] Place the bearing layer in the cavity of the tooling bottom mold so that the inner surface fits with the bottom model surface and fix it with the edge pressure stop block. Then try to assemble the outer heat protection layer and use the edge pressure stop block as a pre-positioning reference to determine the circumferential edge position for alignment, positioning and adjustment.

[0173] Step 4: Bonding and molding:

[0174] Apply KH-CP silicone rubber adhesive with a total thickness of 0.5 mm evenly on the bonding surface of the bearing layer and the outer heat protection layer, place the outer heat protection layer on top of the bearing layer, use the second positioning reference to position it, fix the position of the outer heat protection layer after assembling it into place, close the upper mold of the tooling and install it on the press.

[0175] Step 5: Pressurized curing with a bonding pressure of 2 MPa to complete the bonding and forming of the heat-resistant and load-bearing integrated composite component.

[0176] Step 6: Demolding:

[0177] After curing at room temperature for 72 hours, open the upper mold, loosen the fastening screws of the edge pressure limit block and the middle wedge-shaped positioning block respectively, take out the positioning block, clean the residual adhesive and perform local trimming to obtain the bonded product.

[0178] Implementation Effect

[0179] The prepared flexible buffer material has a strength of 3.2 MPa, an elongation of 340%, and an elasticity of 80%.

[0180] The product was tested using CT and the bonding quality of the bearing layer and the outer heat protection layer was good, with no debonding areas, the effective bonding area ratio was 100%, and the structures of the outer heat protection layer and the bearing layer were intact without any internal damage.

[0181] Comparative Example 1

[0182] A commercially available low-elastic polyurethane rubber layer is used as the flexible buffer material, with a strength of 1.2MPa, an elongation of 100%, and an elasticity of 40%.

[0183] The preparation process of the flexible buffer material is omitted, and the flexible buffer material disclosed in the present invention is replaced with a commercially available low-elastic polyurethane rubber layer to make the tooling buffer pad. Other operations and parameter settings are exactly the same as those in Example 1.

[0184] Implementation Effect

[0185] When the product was tested using CT, the bonding quality between the load-bearing layer and the outer heat protection layer was poor, with large areas of debonding and the effective bonding area accounting for only 80%.

[0186] Comparative Example 2

[0187] A commercially available high-elastic rubber layer is used as the flexible buffer material, with a strength of 2.2MPa, an elongation of 240%, and an elasticity of 60%.

[0188] The preparation process of the flexible buffer material is omitted, and the flexible buffer material disclosed in the present invention is replaced with a commercially available high-elastic rubber layer to make the tooling buffer pad. Other operations and parameter settings are exactly the same as those in Example 1.

[0189] Implementation Effect

[0190] The product was tested using CT and the bonding quality between the load-bearing layer and the outer heat protection layer was good, with an effective bonding area ratio of 94%. However, the outer heat protection layer had local delamination and fracture, and the internal structure was damaged.

[0191] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A flexible cushioning material, characterized in that: The flexible buffer material has a three-layer structure stacked in the order of a flexible rubber layer (1), a fiber-reinforced composite sandwich core, and a wear-resistant rubber layer (5); Wherein, the fiber reinforced composite sandwich core comprises multiple gradient density units.

2. The flexible cushioning material according to claim 1, characterized in that: The fiber-reinforced composite sandwich core is made of a fiber preform and resin.

3. The flexible cushioning material according to claim 2, characterized in that: The fiber preform is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber.

4. The flexible cushioning material according to claim 2, characterized in that: The resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, organosilicon-modified phenolic resin, boron phenolic resin and polyarylacetylene resin.

5. The flexible cushioning material according to claim 1, characterized in that: The density is lowest at the junction of the fiber-reinforced composite sandwich core and the flexible rubber layer (1), and the density is highest at the junction of the fiber-reinforced composite sandwich core and the wear-resistant rubber layer (5).

6. The flexible cushioning material according to claim 1, characterized in that: The total thickness of the flexible buffer material is 0.6-1.0 mm, the thickness of the flexible rubber layer (1) and the wear-resistant rubber layer (5) are respectively 0.15-0.25 mm, and the thickness of the fiber-reinforced composite sandwich core is 0.3-0.5 mm.

7. A method for preparing the flexible cushioning material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: prepare a flexible rubber sheet; S2: preparing fiber preforms of different volume densities, cutting them into suitable sizes and stacking them in order of volume density as gradient reinforcements; diluting the resin with a solvent, injecting it into the gradient reinforcements, and obtaining a fiber-reinforced composite sandwich core after drying; S3: prepare wear-resistant rubber sheet; S4: placing the cut flexible rubber sheet, the fiber-reinforced composite sandwich core, and the wear-resistant rubber sheet in the vulcanization mold in sequence, and obtaining the flexible cushioning material after vulcanization and demoulding.

8. The preparation method according to claim 7, characterized in that: The step S2 comprises: diluting the resin with a solvent to a mass concentration of 10-50%, controlling the injection pressure to 0.01-0.15 MPa, and injecting the diluted resin into the gradient reinforcement body.

9. A tool for integrally forming a composite component, characterized in that: The tooling consists of an upper mold, a buffer pad, and a bottom mold, wherein the buffer pad is made of the flexible buffer material described in any one of claims 1 to 6 or is made of the flexible buffer material prepared by the preparation method described in any one of claims 7 to 8.

10. An application of the tooling according to claim 9, characterized in that: By using the tooling, the integrated molding of the composite component is achieved through material surface treatment, adhesive coating, pressurization curing, and demoulding steps.

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